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Re: how to count the number of ipv6 addresses in a range?

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On 30.03.2015 18:43, Mateusz Viste wrote:
> Hello group,
>
> Today I got into troubles with an old piece of code that was working very well on an
> "inet" column when the column was used for IPv4 addresses, but went south with
> introduction of IPv6 records.
>
> Basically, it's about counting the number of IP addresses in a range:
>
>  > postgres=# select 'a:b:c:dd::'::inet - 'a:b:c:dd::'::inet;
>  >  ?column?
>  > ----------
>  >         0
>  > (1 row)
>
> The above works fine, but if the range becomes greater, then postgres is happy no more:
>
> postgres=# select 'a:b:c:dd::'::inet - 'a:b:c:da::'::inet;
> ERROR:  result is out of range
> postgres=#
>
> Question to you guys - is there some "clean" way to deal with this? I naively tried
> casting the result in such way:
>
>  > select ('a:b:c:dd::'::inet - 'a:b:c:da::'::inet)::NUMERIC(30);
>
> But this won't help. Any kind ideas? I'm running a Postgres 8.4 cluster, but tested
> on a v9.3.2 with same sad results.
>
> cheers,
> Mateusz

well, looking at

     'a:b:c:dd::'::inet - 'a:b:c:da::'::inet

let's find out the size of the difference.

The prefix aa:b:c:dd is 32 bits long, subtract this from 128 to get a remaining 
length of 96 bits.

Add to this the difference 0xd - 0xa, so the result has at least 98 bits. This can be 
handled only with bignum support.

I would raise this on a postgresql mailing list, for example
www.postgresql.org/list/pgsql-general/

You can read the lists with a newsreader, for example
     news://news.gmane.org:119/gmane.comp.db.postgresql.general

/Str.

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how to count the number of ipv6 addresses in a range? Mateusz Viste <mateusz.viste@localhost> - 2015-03-30 18:43 +0200
  Re: how to count the number of ipv6 addresses in a range? "M. Strobel" <strobel@example.com> - 2015-03-30 22:13 +0200
    Re: how to count the number of ipv6 addresses in a range? "M. Strobel" <strobel@example.com> - 2015-03-31 01:25 +0200
    Re: how to count the number of ipv6 addresses in a range? Mateusz Viste <mateusz.viste@localhost> - 2015-03-31 09:39 +0200
      Re: how to count the number of ipv6 addresses in a range? "M. Strobel" <strobel@example.com> - 2015-03-31 09:56 +0200
        Re: how to count the number of ipv6 addresses in a range? Mateusz Viste <mateusz.viste@localhost> - 2015-03-31 11:03 +0200
      Re: how to count the number of ipv6 addresses in a range? Ralf Döblitz <doeblitz@doeblitz.net> - 2015-04-02 16:48 +0000
        Re: how to count the number of ipv6 addresses in a range? Mateusz Viste <mateusz.viste@localhost> - 2015-04-03 09:09 +0200
          Re: how to count the number of ipv6 addresses in a range? Ralf Döblitz <doeblitz@doeblitz.net> - 2015-04-03 13:17 +0000

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